def from_arc(cls,
arc: ConstructionArc,
start_width: float,
end_width: float,
segments: int = 64) -> 'CurvedTrace':
"""
Create curved trace from an arc.
Args:
arc: :class:`~ezdxf.math.ConstructionArc` object
start_width: start width
end_width: end width
segments: count of segments for full circle (360 degree) approximation, partial arcs have proportional
less segments, but at least 3
Raises:
ValueError: if arc.radius <= 0
"""
if arc.radius <= 0:
raise ValueError(f'Invalid radius: {arc.radius}.')
curve_trace = cls()
count = max(math.ceil(arc.angle_span / 360.0 * segments), 3) + 1
center = Vec2(arc.center)
for point, width in zip(arc.vertices(arc.angles(count)),
linspace(start_width, end_width, count)):
curve_trace._append(point, point - center, width)
return curve_trace
def test_vertices():
angles = [0, 45, 90, 135, -45, -90, -135, 180]
arc = ConstructionArc(center=(1, 1))
vertices = list(arc.vertices(angles))
for v, a in zip(vertices, angles):
a = math.radians(a)
assert v.isclose(Vec2((1 + math.cos(a), 1 + math.sin(a))))